In water-cooled nuclear reactors, such as pressurized water reactors (“PWRs”), water is continuously fed into the core of the reactor. The water is continuously replenished from a makeup water source, such as, a Primary Makeup Water (“PMW”) System. The water may contain at least one chemical, such as, boron which is used to control the neutron flux inside the reactor core.
The PMW System typically includes a primary water storage tank for containing the makeup water. The makeup water in the primary water storage tank is usually covered (e.g., with a rubber bladder) to prevent air from entering the storage tank. However, it has been found that even with a covering, there is still an amount of air that can enter the storage tank. It is desired to prevent air from entering the storage tank because air contains gases, such as, nitrogen, oxygen and argon, which can dissolve in the water. The makeup water including the dissolved gases is then ultimately fed into the reactor core and, related systems and components. This can be a concern because dissolved gases, such as, oxygen, are known sources of corrosion in water systems. It is known in the art to add chemicals, such as, hydrazine, to the makeup water to control the dissolved oxygen level therein. However, there are disadvantages associated with the addition of hydrazine. For example, hydrazine can breakdown and, as a result, increase the amount of dissolved nitrogen in the makeup water. Further, a nitrogen blanket may be used in the primary water storage tank, which can also increase the amount of dissolved nitrogen in the makeup water. It has been found that when the makeup water is ultimately fed into the reactor core, the dissolved nitrogen in the makeup water can increase the production of carbon-14. The nitrogen forms carbon-14 when it absorbs neutrons in the core of the reactor. It is known that carbon-14 is an environmental contaminant and therefore, it is desirable to minimize or preclude its formation. Additionally, argon has undesirable effects similar to nitrogen and therefore, it is preferred to remove at least one of dissolved oxygen, nitrogen and argon from the makeup water.
Thus, there is a need to design and develop improved systems and methods for controlling, e.g., reducing, minimizing or removing, the level of dissolved gases in makeup water that is ultimately fed into the core of a water-cooled nuclear reactor or related systems. Further, it is desired to provide systems and methods that can be employed on-demand such that the PMW System can be in a standby or non-operational mode when not needed and can be initiated or started-up in response to the occurrence of a situation or event which requires makeup water to be supplied.